1. Technical Field
The present invention relates to secondary optics for photovoltaic devices, and more particularly to solar concentrators to homogenize an optical spectrum and intensity of incident solar radiation imaged into a light pipe.
2. Description of the Related Art
Solar concentrators operate by focusing the light on a photovoltaic cell. Employing optical devices to concentrate the light on the photovoltaic cell enables the concentrator to operate at high power density levels. A Concentrator Photo-Voltaic (CPV) system employs an efficient photovoltaic element to convert concentrated incident light energy to electricity. Some CPV systems employ a triple junction photovoltaic cell and receiver to accomplish this conversion. The cell converts the wavelength spectrum of the sun in three wavelength regions of the cell. Each region of the spectrum is absorbed in a selected semiconductor material that efficiently converts the optical power in that spectrum region into electrical power.
Efficient CPV systems often use two concentration elements for most efficient light concentration, primary and secondary. The primary element typically comprises one of a Fresnel lens and a focusing mirror. The primary element collects the sun light and focuses the light onto an image in the secondary optic through which the light travels to the photovoltaic cell. The secondary optic may include a light pipe. A light pipe (or light prism) includes a solid piece of glass having surfaces with smooth optical quality finishes, also referred to as a non-imaging optical element. The light pipe further concentrates the imaged light from the primary optic onto an area precisely matching the area of the cell. However, conventional simple light prisms commonly used in the industry are not optimal in uniformity of intensity and homogeneity of spectral content.